1. Field of the Invention
The present invention relates generally to methods and compositions that are used to control the rate at which cells proliferate and their capacity for proliferation. More particularly, the present invention involves methods and compositions which are used to increase cell proliferation in a completely reversible way without causing the cells to become malignant or otherwise affecting the cells.
2. Description of Related Art
Many diseases involve the degeneration of specific cells. Such diseases include Duchenne's muscular dystrophy, insulin dependent diabetes mellitus, Parkinson's disease, Huntington's disease, Alzheimer's disease, olivopontocerebellar atrophy and many others. A suggested treatment for these diseases involves removing cells from relatives and introducing them into the patient. However, rejection of the foreign cells is and will be a recurrent problem with such a proposed treatment approach (Partridge, T.A., et al. (1989)). Nature 337:176-179). ( Another approach to treating the above-identified diseases is to use the patient's own cells. Use of the patient's own cells allows a perfect immunological match and therefore overcomes any problems associated with rejection of the cells. In such processes, the patient's cells are removed from the patient, grown in vitro, genetically engineered to produce the appropriate protein, and reintroduced to the patient.
A major problem with the above approach is that tumor suppressor genes are expressed in all normal (non-cancerous) cells. These tumor suppressor genes express proteins that inhibit growth of cells. Viruses and transforming genes have been used to bind the inhibiting proteins and thereby effect proliferation of cells.